There are conventionally known navigation devices and navigation systems for searching a route from a desired departure point to a destination and providing guidance to a user using map data and road data, and examples of such navigation devices and navigation systems that have been implemented include car navigation devices that are mounted in an automobile and that provide route guidance to a driver, and communication-type navigation systems that send route search requests to a route search server and receive the results to receive route guidance using a mobile phone as a terminal device for navigation.
In particular, a communication-type navigation system is also used as a navigation system for pedestrians. There are also navigation systems for pedestrians that preferably have a route guidance function that includes modes of transportation and have, in addition to searching and providing guidance for walking routes, a function for collecting operation timetable data and routes for railroads, airplanes, buses, and other modes of transportation, and for providing guidance for routes (boarding-candidate train) from a desired departure station to a desired destination station in addition to searching and providing guidance of walking route. There are also transportation guide systems for receiving and displaying routes for modes of transportation, timetables, boardable trains, and other distributed information from an information distribution server that does not provide route searches for walking routes.
Route search devices and route search methods used in general navigation devices and communication navigation systems are disclosed in, e.g., Patent Document 1 (Japanese Laid-open Patent Application No. 2001-165681). This navigation system is configured so as to send departure point and destination information from a mobile navigation terminal to an information distribution server, search from road network and transportation network data in the information distribution server, and provide guidance for a route that matches the search conditions. Used as one search condition for a route search is movement means from a departure point to a destination, examples of which include walking, automobile, railroad, aircraft, and other modes of transportation in combination with walking.
The information distribution server uses the positions of connecting points and curve points of roads (routes) in a map data as connection points as nodes, and the route that connects the nodes as links, and is provided with cost information (distance, time required) of all the links as a database. The information distribution server references the database, and is capable of sequentially searches for links that reach from the node of the departure point to the node of the destination, following nodes and links that minimize the cost information of links, and providing guidance to the mobile navigation terminal about the shortest route. A method referred to as the label determination method or the Dijkstra method is used as the route search technique. A route search method that uses the Dijkstra method is disclosed in Patent Document 1 noted below.
Route search systems for searching routes using transportation systems are provided with an operation timetable database in which operation timetable data of transportation systems have been organized into a database on the basis of departure time, departure point, destination, arrival time, and other route search conditions specified by the user; and are provided with data in which the transportation network has been organized into a database on the basis of the above. The route search systems are configured to reference these databases, connect a departure point and a destination that includes transit changes (transfers), sequentially follow usable modes of transportation (individual trains and shuttle buses) as a route, and present one or a plurality of candidates for route guidance (departure station, destination station, course, train, and other modes of transportation) that matches the route search conditions. Route search conditions that can be specified commonly further include required time, number of transit changes, fares, and other conditions.
Map data and route search network data provided to a common routing guide system is data related to a region (referred to herein as service area) to which the system provides routing guide service. For example, an ordinary routing guide system is designed for domestic service in a certain country, or is designed for service in a specific region in a certain country.
In such a case, there is no problem in a route search or route guidance as long as the departure point and destination are within the service area of a certain routing guide system. However, the total route cannot be search or guidance provided from a departure point to a destination in the case that the departure point is within a certain country and the destination is located in another country. The reason for this is that the route that the routing guide system on the departure point side can search and provide guidance for has a range that lies within the country of the departure point side, and is not provided with map data and route search network data of the other country of the destination side.
In an onboard navigation device or the like, map data and route search network data of a specific region are stored in the onboard navigation device; and when a geographical point outside of the area is set as the destination, the route search depends on a server provided with map data and route search network data of the entire country that includes the other region. Alternatively, a method may be used in which a route search is enabled on the navigation device side by downloading the map data and route search network data of the lacking regions.
For example, such a routing guide device has been disclosed in Patent Document 2 noted below (Japanese Laid-open Patent Application 2003-97960). The routing guide device uses starting points midway in the route as a plurality of candidates when route search from the departure point to the destination is carried out in a central facility. When the starting points are transmitted to the routing guide device, the routing guide device determines and transmits to the central facility the starting points for which guidance can be provided. The central facility carries out a route search from the departure point to the starting points, and the guide device is designed to carry out a route search from the starting points to the destination and provide an optimal route from the departure point to the destination.    [Patent Reference 1]: Japanese Laid-open Patent Application No. 2001-165681 (FIGS. 1 and 2)    [Patent Reference 2]: Japanese Laid-open Patent Application No. 2003-97960 (FIGS. 1 and 2)